First of all, we must see the need for propitiation. In all of the places where propitiation is mentioned, the context is dealing with sins. We have a sin problem. The trouble is that we keep sinning. Even when we are not sinning, we lean towards sin because we have a sin nature.

1 John 2:2And he is the propitiation for our sins: and not for our's only, but also for the sins of the whole world.
See All... says, “And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world.”

1 John 4:10Herein is love, not that we loved God, but that he loved us, and sent his Son to be the propitiation for our sins.
See All... says, “Herein is love, not that we loved God, but that he loved us, and sent his Son to be the propitiation for our sins.” 

Notice that propitiation takes care of our sins.

Romans 3:25Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God;
See All... says, “Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God;”

This use of propitiation also deals with sins. In fact, this verse is a continuation of a sentence that began in verse 23, which says, “For all have sinned, and come short of the glory of God;” 

There is a sin problem in this world and that sin problem infects every individual who lives in this world. You are born with a natural tendency to sin. You like to rebel. Watch children as they grow up. When mommy and daddy tell them not to do something, what is their natural tendency? Do they automatically want to obey? No! They have a sin nature that goes all the way back to Adam. They, and you, like to sin. Your flesh likes the things of this world. It likes to eat too much and look at things it ought not look at. It likes to fuss and complain. It likes to listen to gossip and pour it out of your mouth. It enjoys those things! Praise God for salvation, but we need to understand where we come from.

We like to take atheists to Psalm 14:1The fool hath said in his heart, There is no God. They are corrupt, they have done abominable works, there is none that doeth good.
See All... where it says, “The fool hath said in his heart, There is no God. They are corrupt, they have done abominable works, there is none that doeth good.” We say, those fools say there is no God, and they are corrupt, and there is none of them that do good—but read a little further. 

In verses two and three, it says:

“The LORD looked down from heaven upon the children of men, to see if there were any that did understand, and seek God. They are all gone aside, they are all together become filthy: there is none that doeth good, no, not one.”  

God applies this to all men. You cannot get saved until you realize you are lost. You cannot realize you are lost until you know that you are a sinner and that your own sin condemns you. Many false teachers are telling people that they are good and that everyone is good in his or her heart. The Bible does not say that. It says that everyone is evil in his heart by his own nature. People do not like to hear this but it is the truth as found in God’s holy word.

The teaching that everyone is good does not come from the word of God. It comes from the evil hearts of men. They say everybody is good because they deny that Book! If you believe the Bible, then you believe that we are sinners by nature and sinners by practice.

In Jeremiah 17:9The heart is deceitful above all things, and desperately wicked: who can know it?
See All..., the Bible says, “The heart is deceitful above all things, and desperately wicked: who can know it?” The next verse (Jeremiah 17:10I the LORD search the heart, I try the reins, even to give every man according to his ways, and according to the fruit of his doings.
See All...) says that God knows the heart. He is the only one who knows just how deep and dirty our hearts are. He knows that the heart is deceitful above all things.

Isaiah 64:6But we are all as an unclean thing, and all our righteousnesses are as filthy rags; and we all do fade as a leaf; and our iniquities, like the wind, have taken us away.
See All... says, “But we are all as an unclean thing, and all our righteousnesses are as filthy rags; and we all do fade as a leaf; and our iniquities, like the wind, have taken us away.”

You may ask, “Where is the blessing in this information?” The blessing is that someone has taken care of that dirty, dark sin. But until you realize it is there, you cannot be saved. You have to be lost in order to get saved.  A lot of people have never realized that they are lost.

You must understand the utter sinfulness of man. Man is completely wicked. He is all parts evil. Even when he does good things, he does them for his own selfish nature.  He does them to make himself feel good, and to make himself feel a little bit superior to other people. Or, he does them because of what he expects to get out of them. The prideful, sinful nature that makes man commit crimes is the same nature that causes him to do good works! There is no way out for man, unless it is God’s way.